This invention relates to the generation of electric power from solar radiation, and more particularly relates to photovoltaic arrays and similar devices in which solar radiation passes through a set of lenses that focus the radiation onto a set of solar cells that generate electricity.
The following publications of the Electric Power Research Institute are representative of the prior art and are hereby incorporated in their entirety by reference: "High-Concentration Photovoltaic Module Design," EPRI AP-4752, Aug., 1986; "Conceptual Design for a High-Concentration (500X) Photovoltaic Array," EPRI AP-3263, Dec., 1984; and "Point-Contact Silicon Solar Cells," EPRI AP-2859, May, 1983.
As disclosed in these publications, a typical photovoltaic array is constructed of a set of 60 "modules" in the form of rectangular metal boxes. The top surface of each module includes a pair of lens assemblies or "parquets." Each lens "parquet" is a transparent sheet that includes a set of 24 lenses that focus solar radiation onto a set of respective solar cells located inside the module. The peripheries of the lens parquets are fitted with polymer seals to reduce leakage of water into the module. The 60 modules are mounted onto a structural grid to form the photovoltaic array, the structural grid being supported by a vertical pedestal post.
Inside each module, each of the 24 solar cells forms part of a respective cell package. Each cell package consists of a metal mounting plate that functions as a heat spreader, a flat, ceramic electrical insulator that is soldered on top of the mounting plate, a pair of electrodes that are soldered on top of the electrical insulator and are electrically isolated from the mounting plate, a flat, silicon solar cell that is soldered on top of the pair of electrodes and is thereby electrically connected to the electrodes, and a four-sided, prismatic reflector or "secondary optical element" that is bonded to the top of the solar cell and that directs, by means of reflection, solar radiation that would otherwise miss the active area of the cell toward the active area of the solar cell.
Inside each module, four solar cells connected in series are connected in parallel with four other solar cells connected in series. There are six such sets of eight solar cells, the six sets being connected in series.